Various polymerization processes are usually carried out in large vessels or reactors having a stirring or agitation means mounted therein and also, are frequently provided with auxiliary euipment, such as baffles, and the like. In many cases, such processes eventually produce undesirable polymer deposits on the internal surfaces of the reactor during the course of the polymerization reaction. Such deposits interfere with the efficient transfer of heat to and from the interior of the reactor. Further, these polymer deposits or buildup have a tendency to deteriorate and to partially fragment resulting in contamination of the reaction mixture and the products produced therefrom. This buildup of solid polymer on reactor surfaces not only interferes with heat transfer, but also decreases productivity and adversely affects polymer quality.
This problem is particularly bad in the commercial production of polymers and copolymers of vinyl and vinylidene halides, when polymerized alone or with other vinylidene monomers having a terminal CH.sub.2 .dbd.C&lt; group, or with polymerizable polyolefinic monomers. For example, in the commercial production of vinyl chloride polymers, the same are usually produced in the form of discrete particles by polymerization in aqueous suspension systems. When employing such a polymerization system, the vinyl chloride, and other comonomers when used, are maintained in the form of small discrete droplets by the use of suspending agents and agitation. When the reaction is complete, the resultant polymer is washed and dried. These aqueous suspension system polymerization reactions are usually conducted under pressure in metal reactors equipped with baffles and high speed agitators. However, these suspension systems have a tendency to be unstable and during the polymerization reaction, vinyl chloride polymer, such as polyvinyl chloride (PVC) builds up on the interior surfaces of the polymerization reactor, including the surfaces of the baffles and agitator. Obviously, the polymer buildup must be removed since it results in further formation of polymer buildup which in turn results in a crust that adversely affects heat transfer and contaminates the polymer being produced.
The nature of the polymer buildup, or insoluble deposit on the walls of the reactor, is such that in the commercial production of polymers, as described above, it has in the past been standard practice, after each polymerization reaction is completed, to open the reactor and scrape the polymer buildup off the walls and off the baffles and agitator. An operation such as this is not only costly, both in labor and down-time of the reactor, but presents potential health hazards as well. While various methods have heretofore been proposed to reduce the amount and nature of polymer buildup on polymerization reactor surfaces, such as solvent cleaning, various hydraulic and mechanical reactor cleaners, and the like, none has proved to be the ultimate in polymer buildup removal. That is to say, these various methods and apparatus have done an acceptable job, but there is still room for improvement in this area, particularly from an economic point of view.
It is also known to coat the internal surfaces of reactors with various chemical substances in coating solutions to prevent buildup of polymer on said surfaces. Many of these coating solutions give excellent results. However, for purposes of economics and ease of handling, it would be most desirable to have a material soluble in water which, when applied to the internal surfaces of a reactor from a water solution, would prevent polymer buildup thereon.